Water dispersible adhesive compositions

ABSTRACT

Disclosed is an essentially odorless water dissipatable or dispersible adhesive composition that is useful in forming paper articles and other products that can be recycled through repulping in both neutral and alkaline media. The water dispersible adhesive composition is preferably a hot melt adhesive that is a low molecular weight, branched copolyester containing a sulfomonomer. The copolyester adhesive composition can be used neat or formulated and exhibits broad compatibility with a variety of adhesive additives, including non polar tackifiers.

This is a divisional application of application Ser. No. 08/519,958,filed Aug. 28, 1995, now U.S. Pat. No. 5,744,538.

FIELD OF THE INVENTION

The present invention is directed to water-dispersible adhesivecompositions. More particularly, the present invention is directed to anessentially odorless formulated hot melt adhesive composition that, dueto its water-dispersibility, allows paper products, nonwoven assemblies,and other disposable products to be more effectively recycled. Thepresent invention is also directed to aqueous adhesive compositions andemulsions containing polyester and hot melt compositions containingpolyester, tackifier and oils which are water dispersible whilemaintaining excellent adhesive properties.

BACKGROUND OF THE INVENTION

Many adhesives including, hot melt adhesives are useful for bondingvarious substrates together such as wood, paper, plastics, nonwovenassemblies, and textiles, as well as other materials. One use for whichthey are well suited is the fabrication of corrugated paper board. Hotmelt adhesives, useful for producing corrugated paper board, must havehigh bond strength under conditions of shock, stress, high humidity, andextremes of temperature encountered in transportation and storage. Inaddition, the melt point, wetting time, initial tack, setting time, potlife, and general handling qualities on automatic corrugated boardmachinery are essential considerations.

At present, it is very desirable to recycle paper, paper products, andother disposable products to conserve material resources and to avoidlarge additions to landfill space. It is thus a general practice in thepaper industry to recover at least a portion of the used and wastecorrugated material and repulp the material for use in the preparationof other materials such as cardboard. The use of polyolefin hot meltadhesives to close or seal cartons made from corrugated material haspresented problems in regard to repulpability of the used boxes orcartons (see U.S. Pat. Nos. 4,070,316; 4,127,619; 4,146,521; 4,460,728;4,471,086; and 4,886,853). In fact, all the presently available hot meltand pressure sensitive adhesives are largely water insoluble and verydifficult to disperse during the repulping process. This fact makescertain paper products, in which adhesives are necessarily utilized,unattractive since failure to disperse the insoluble adhesives resultsin lower quality recycled paper having variable composition andnon-uniformity and thus, lower product value.

One approach to avoid the presence of insoluble adhesives in therecycled paper products is to use adhesives whose density is differentfrom the density of water and pulp in water, thus permittinggravitational separation. However, this requires separation steps whichcan increase the recycling costs of the paper products containingadhesives.

Presently available water soluble or dispersible "natural" adhesivessuch as dextrins, cellulose gums, and animal glues derived from thehides and bones of animals have lower strength, fail to adhere well topaper and wood stocks with coatings or heavy ink applications, andsometimes require special treatment and handling because of their highviscosity. Therefore, the use of these adhesives, which may be easilyrecyclable, is quite low due to poor adhesive characteristics. Attemptsto produce synthetic water-dispersible hot melt adhesive compositionshave heretofore been unsuccessful due to resulting poor adhesiveproperties such as thermal stability, low strength, poor viscosities andlow cold flow resistance. Additionally, costs and ease in manufacturinghave precluded their use (see U.S. Pat. Nos. 3,919,176 and 5,098,962).

In addition to paper and paper products there are many disposableproducts, such as diapers, tampons, and sanitary napkins, in which hotmelts and other types of adhesives are used. The use of current hot meltadhesives in these products complicate attempts to recycle products andseparate out the insoluble sticky hot melt adhesives.

Copending application SN 08/283,011 filed Jul. 29, 1994 solves theseproblems and discloses water-dispersible aqueous or hot melt adhesivesthat maintain the desirable properties of presently available hot meltadhesives.

However, the specific adhesives disclosed in this copending application08/283,011 are not compatible at higher concentrations with nonpolaradditives such as hydrocarbon tackifing resins and naphthenic/paraffinicoils. Additionally, it would be very desirable to produce an adhesivecomposition that is essentially odorless.

SUMMARY OF THE INVENTION

A water-dispersible adhesive composition according to the presentinvention comprises a branched water-dispersible copolyester compositionmade of the residues or moieties of reaction products;

(I) 1,4-cyclohexanedicarboxylic acid;

(II) about 2 to 40 mol percent, based on the total of all acidequivalence, of at least one difunctional sulfomonomer containing atleast one sulfonate group bonded to an aromatic ring wherein thefunctional groups are carboxyl or esters thereof;

(III) at least one diol or a mixture of diols comprising:

(A) about 0.1 to 85 mol percent, based on the total mol percent of diolmoieties having the formula H(--OCH₂ CH₂ --)_(n) OH wherein n is 2 toabout 20 provided that the mol percent of such moieties is inverselyproportional to the value of n;

(B) about 0.1 to 15 mol percent, based on the total mol percent of diolmoieties of a poly(ethylene glycol) having the formula H(--OCH₂ CH₂--)_(n) OH wherein n is 2 to about 500, provided that the mol percent ofsuch moieties is inversely proportional to the value of n; and

(C) 0 to about 99 mol percent of the diol component being selected fromthe group consisting of glycols containing two --C(R¹)₂ --OH groupswherein R¹ in the reactant is a hydrogen atom, an alkyl of 1 to 5 carbonatoms, or an aryl group of 6 to 10 carbon atoms;

(IV) 0 to about 40 mol percent of a hydroxycarboxylic acid having one--C(R--)₂ --OH group, wherein R in the reactant is hydrogen or an alkylgroup of 1 to 6 carbon atoms; and

(V) about 0.5 to 40 mol percent of a "multifunctional" or"branch-inducing" reactant containing at least three functional groupsselected from hydroxyl, carboxyl, and mixtures thereof;

the copolyester containing substantially equal mol proportions of acidequivalents (100 mol percent) and diol wherein the inherent viscosity isat least 0.1 dL/g measured in a 60/40 parts by weight solution ofphenol/tetrachloroethane at 25° C. and at a concentration of about 0.25g of copolyester in 100 ml of the solvent, the glass transitiontemperature T_(g) is no greater than 20° C., and the ring and ballsoftening point is at least 70° C.

The present invention further comprises the copolyester above in anadhesive formulation that comprises a mixture of

(a) 20 to 80 weight percent of the above copolyester, comprised of theabove amounts of moieties I, II, III, IV and V;

(b) about 2 to 60 weight percent of a tackifier selected from the groupconsisting of terpene resins, aromatic resins, aliphatic hydrocarbonresins, rosins, and functionalized polymers;

(c) about 0 to 30 weight percent of an extending oil selected from thegroup consisting of paraffinic oils, naphthenic oils, liquid polyesters,liquid hydrocarbon resins, liquid rosins, low molecular weightpolyethylene glycols, dibenzoates, isobutyrates, phthalate oils, animaloils, vegetable oils, and mineral oils; and

(d) about 0.1 to about 2 weight percent of a stabilizer.

DETAILED DESCRIPTION OF THE INVENTION

The applicants have unexpectedly discovered an improved adhesive thatnot only has excellent hot melt adhesive properties and is totallydispersible but is also essentially odor free and very compatible withtackifying resins including nonpolar tackifying resins, even at higherconcentrations. The present adhesive composition can be applied as aliquid dispersion (aqueous or solvent) on substrates as well as by hotmelt applications.

The present adhesive composition is completely dispersible and can beremoved from the fibers from paper or wood pulp used in disposableproducts. The hot melt adhesive according to the present inventionpermits recycling of disposable products at significantly reducedprocessing costs without affecting the physical properties of theadhesive and resulting article.

The water-dispersible polyester composition of the present invention hasan inherent viscosity of at least 0.1, preferably, 0.2 dL/g, morepreferably about 0.28 to 0.65 dL/g, and most preferred about 0.4 to 0.6dL/g measured in a 60/40 parts by weight solution ofphenol/tetrachloroethane at 25° C. and at a concentration of about 0.25g of polymer in 100 ml of solvent.

In the water dispersible adhesive composition of the present invention,(I) 1,4-cyclohexanedicarboxylic acid is preferably in a concentration toequal about 100 mol percent of the acid component when in combinationwith a dicarboxylic acid sulfomonomer. However, component (I) can alsocontain up to 10 mol percent, based on a total of 100 mol percent acid,of difunctional dicarboxylic acids other than1,4-cyclohexanedicarboxylic acid selected from the group consisting ofaliphatic dicarboxylic acids, alicyclic dicarboxylic acids, aromaticdicarboxylic acids, and mixtures of two or more of these acids. Examplesof preferred suitable dicarboxylic acids include succinic; glutaric;adipic; azelaic; sebacic; fumaric; maleic; itaconic;1,3-cyclohexanedicarboxylic; 1,3-cyclohexanedicarboxylic; phthalic;terephthalic; and isophthalic. The 1,4-cyclohexanedicarboxylic acid of(I) is preferably in a concentration of about 50 to 95 mol percent basedon the total acid equivalents, more preferably 60 to 90 mol percent,with a mol percent of about 70 to 90 being most preferred.

The difunctional sulfo-monomer component of (II) is preferably adicarboxylic acid or ester thereof containing a metal sulfonate group.The cation of the sulfonate salt is preferably monovalent and can be NH₄⁺, or the metal ions Li⁺, Na⁺, K⁺ and the like.

Residue or reactant (II) in the polyester of the present invention is adifunctional monomer containing a --SO₃ M group attached to an aromaticnucleus, wherein M is hydrogen, NH₄ ⁺, or a metal ion. The cation of thesulfonate salt group can be NH₄ ⁺, or the metal ions Li⁺, Na⁺, K⁺ andthe like.

The --SO₃ M group is attached to an aromatic nucleus, examples of whichinclude benzene, naphthalene, anthracene, diphenyl, oxydiphenyl,sulfonyldiphenyl, and methylenediphenyl.

The cationic portion of a nonmetallic sulfonate group optionally presentin reactant (II) is a nitrogen-based cation derived fromnitrogen-containing bases which may be aliphatic, cycloaliphatic oraromatic basic compounds that have ionization constants in water at 25°C. of 10⁻³ to 10⁻¹⁰, preferably 10⁻⁵ to 10⁻⁸. Especially preferrednitrogen-containing bases are ammonia, dimethylethanolamine,diethanolamine, triethanolamine, pyridine, morpholine, and piperidine,due to availability, cost, and usefulness. Such nitrogen-containingbases and cations derived therefrom are described in U.S. Pat. No.4,304,901, the disclosure of which is incorporated herein by referencein its entirety.

The amount of reactant (II) is present in a concentration of about 2 to40 mol percent. The amount of reactant or moiety (II) is preferablyabout 4 to 25 mol percent, with a mol percent of about 6 to 20 beingmost preferred based on total acid equivalents. At amounts below 2 andin some cases below 4 mol percent, the polyester is less repulpablewhereas at amounts above 40 and in some instances above 20 the polyesteris more water sensitive.

Examples of preferred diols of (III) (A), due to availability, includediethylene glycol, triethylene glycol and mixtures thereof. Thepreferred concentration of (III) (A) is about 10 to 80 mol percent;however, when these are the preferred diols of (III) (A) theconcentration is about 10 to 80 mol percent. At amounts outside thisrange of 10 to 80 the polyesters have lower softening points or higherT_(g) than what is generally most preferred.

Examples of suitable poly(ethylene glycols) of (III) (B) includerelatively high molecular weight polyethylene glycols, some of which areavailable commercially under the designation "Carbowax", a product ofUnion Carbide. Poly(ethylene glycols) having molecular weights of fromabout 500 to about 5000 are especially suitable. Moieties of (B), ifused, are preferably in a concentration of about 1 to 5 mol percent,particularly when n is 10 to 30 due the preferably higher softeningpoints.

The remaining portion of the glycol component (III) (C) can be in aconcentration of 0 to 99 mol percent, more preferably about 10 to 60 molpercent. This glycol component can generally be selected from the groupconsisting of aliphatic, alicyclic, and aralkyl glycols. Examples ofthese glycols include ethylene glycol; propylene glycol;1,3-propanediol; 2,4-dimethyl-2-ethyl-hexane-1,3-diol;2,2-dimethyl-1,3-propanediol; 2-ethyl-2-butyl-1,3-propanediol;2-ethyl-2-isobutyl-1,3-propane-diol; 1,3-butanediol; 1,4-butanediol;1,5-pentanediol; 1,6-hexanediol; 2,2,4-trimethyl-1,6-hexanediol;1,2-cyclohexanedimethanol; 1,3-cyclohexanedimethanol;1,4-cyclohexanedimethanol; 2,2,4,4-tetramethyl-1,3-cyclobutanediol; andp-xylylenediol. Copolymers may be prepared from two or more of the aboveglycols. Preferred glycols, due to availability, cost, and usefulness,include ethylene glycol, 1,3-propane diol, 1,4-butane diol, 1,6-hexanediol and cyclohexanedimethanols with 1,4-cyclohexanedimethanol andethylene glycol being most preferred.

The moieties of (IV) are less preferred, due to cost and performance,but they can be present. The concentration of these moieties ispreferably below 20 mol percent, more preferably below 10 mol percent,including zero.

The amount of this branching agent (V) is preferably below 20 molpercent, more preferably about 1 to 10 mol percent with a concentrationof about 2 to 6 mol percent being most preferred. At very high amountsof branching agent the polyester is prone to gelation whereas at lowamounts, such as below 0.5 mol percent, the polyester has poorerperformance and properties.

The polyester adhesive raw material compositions (neat) preferably havea number average molecular weight of about 7,000 to 20,000 morepreferably about 7,000 to 15,000. Although it is desirable to have ashigh a molecular weight as possible to achieve the maximum physicalproperties, such as tensile strength and peel strength, the meltviscosity also increase as molecular weight increases. Therefore, atvery high molecular weights the melt viscosity is too high for manyuseful applications.

The preferred Tg of the polyester adhesive raw material compositionaccording to the present invention is below 20° C. and more preferablyvaries from about -20 to 20° C., with a Tg of about -5 to 5° C. beingmost preferred. The Tg (glass transition temperature) of the adhesivecompositions of the present invention are preferably as low as possible.Thus Tgs below 5° C. and even below 0° C. are preferred. Tgs of greaterthan 0° C. have generally higher ring and ball softening point (RBSP)and heat resistance but are not as flexible. A low Tg means that theadhesive compositions will not be brittle, thus, cartons adheredtogether with the adhesive compositions of the present invention whenimpacted, even at extremely cold temperatures will not shatter and thusmaintain adhesion. However, extremely low Tgs are not easily obtained orat least not easily obtained without greatly affecting some otherproperty, such as lowering the ring and ball softening point.

The polyester adhesive raw material composition according to the presentinvention preferably has a viscosity of about 1,500 to about 90,000centipoise at 350° F. (177° C.), more preferably about 10,000 to 60,000cP at 350° F. (177° C.) due to ease in application.

The ring and ball softening point (RBSP) of the polyester adhesive rawmaterial composition of the present invention is generally at least 70°C., preferably at least 80° C., more preferably 80 to 120° C. The hightemperatures of RBSP are better since this means at higher storagetemperatures delamination will not occur. (High RBSP providesdelamination resistance).

The polyester adhesive raw material compositions according to thepresent invention are particularly useful due to their good combinationof properties and are suitable for use as adhesives for many substrates,particularly when blended with conventional tackifiers and additives.These substrates include non woven assemblies (such as non wovenpolypropylene), paper products (such as paper and paperboard), and woodpulp and are easily recyclable and repulpable. The hot melt adhesivesaccording to the present invention are recyclable/repulpable andimproved over available repulpable hot melt adhesive compositions inthat the set time, temperature sensitivity, compatibility, stability onstorage, shear strength, tensile strength, viscosity, and cold flowresistance are improved.

The adhesive composition according to the present invention, either neator formulated with other components, is applied to one substrate with asecond substrate being placed on top of the adhesive forming an articlehaving the adhesive laminated between two substrates.

The adhesive composition according to the present invention can beapplied in liquid form in solvent or in an aqueous solution at aconcentration of about 10 to 70 weight percent, preferably 20 to 50,with the remainder being solvent or water or mixtures thereof.Surfactants and other additives can also be present to aid in thedispersibility of the adhesive composition. When applied as a solution,the adhesive compositions are generally applied by conventionalprocesses, such as extrusion coating, spray coating, roll coating, brushcoating, dip coating, etc.

The adhesive raw material composition either neat or blended with othercomponents can also be applied as a primer in the liquid form tosubstrates such as paperboard to be later coated with polyolefin films.This dispersion will generally have about 20 to 60 percent solids,preferably about 40 percent solids prior to being coated onto thesubstrate. The extrusion of the molten polyolefin film activates theadhesive properties of the polyester composition allowing thepolyolefins to be extrusion coated onto substrates at lowertemperatures, thus saving energy. In this application the adhesivecomposition contains the copolyester component having a higher IV of atleast 0.4 dl/g. At IVs below 0.4 the primed substrates when stacked tendto block and are not easily separated for later extrusion coating. Thisaqueous dispersion containing the copolyester adhesive composition ofthe present invention can contain other conventional adhesive additivessuch as polymer emulsions, polyethylene emulsions, and resin emulsionsto alter tack and strength properties. Suitable examples ofpolyethylenes used in the polyethylene emulsions include low molecularweight polyethylene waxes such as, Epolene E-20 from Eastman ChemicalCompany.

The adhesive raw material composition can also be applied in coatingformulations to a substrate such as in over print and ink formulations.Particularly useful in these applications are the higher IV copolyestercompositions, even in water based formulations.

The adhesive composition according to the present invention ispreferably formulated with other standard adhesive compounds and used asa hot melt adhesive. The hot melt adhesive composition is preferablyapplied in the melt at a temperature of about 150 to 200° C. to asurface of a substrate and, while remaining molten and pliable, applyinga second surface of a substrate to the water-dispersible hot meltadhesive composition thereby forming an article of manufacture thatcomprises the water-dispersible hot melt adhesive composition laminatedbetween two substrates or two surfaces of a substrate (such as a foldedarticle that forms a container).

The adhesive compositions of the present invention are preferably notcrosslinked since that would impair their water dispersibility andrepulpability. However, they could be crosslinked, to a certain extentwith diisocyanates to improve strength and heat resistance although thisis less preferred.

The adhesive composition according to the present invention can alsocontain standard additives including stabilizers. Suitable stabilizersinclude the antioxidant type and generally consist of stericallyhindered phenols, or sulfur or phosphorous substituted phenols.Representative hindered phenols include:1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxy-benzyl)benzene;pentaerythritoltetrakis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; n-octadecyl3,5-di-tert-butyl-4-hydroxyphenyl) propionate; 4,4'-methylenebis(2,6-di-tert-butylphenol); 4,4'-thiobis (6-tert-butyl-o-cresol);2,6-di-tert-butylphenol;60(4-hydroxyphenoxy)-2,4-bis(n-octylthio)-1,3,5-triazine;di-n-octadecyl-3,5-di-tert-butyl-4-hydroxy-benzylphosphonate;2-(n-octylthi-o)-ethyl 3, 5-di-tert-butyl-4-hydroxybenzoate; andsorbitol hex[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. If used,the stabilizer is present in levels of about 0.1 to 3 percent by weightpreferably about 0.1 to 2 weight percent with about 0.1 to 0.5 beingmore preferred. An especially useful antioxidant is Irganox 1010 (fromCiba-Geigy, Hawthorne, N.Y.) which is a pentaerythritoltetrakis-3(3,5-di-tertiarybutyl-4-hydroxyphenyl)propionate.

Additional additives can be added to raise and lower Tg and RBSP. Theseinclude, for example, elastomers, extending oils, low molecular weightpolyolefins, and tackifiers (e.g. tackifying resins). Although,elastomers can be added to the polyester composition, the presence ofsuch elastomers may be adverse to certain desired properties of thecomposition. Therefore, it is preferable that the composition of thepresent invention contain substantially no elastomer. Additionally, theplasticizers such as DOP, DOTP, isobutyrates, phenols, glycols,phthalate esters and the like that can be added, can distract from theheat resistance of the final composition lowering the RBSP.

Other additives such as UV light absorbers, nucleating agents,colorants, pigments, solvents, and fillers can be present in smallamounts as needed and known in the adhesive art.

Tackifiers are added to the copolyester composition to prevent cold flowand increase the softening point. Tackifiers are typically selected fromat least one of the groups consisting of aliphatic hydrocarbon resins,aromatic resins, synthetic polyterpenes or terpene resins,functionalized polymers, and rosins. These tackifing resins, preferablyhave softening points of at least 100° C. and most preferably at least120° C. These tackifing resins can be used alone or in combination andcan be used in amounts of about 2 to 60 weight percent, preferably about10 percent to 55 percent by weight of the adhesive composition, morepreferably about 25 percent to about 50 percent by weight. In someinstances in which greater thermal stability is desired, lower amountsof tackifiers are desired, such as below 40 weight percent.

Aliphatic hydrocarbon resins are disclosed in U.S. Pat. Nos. 3,850,858and 3,701,760. These are generally low molecular weight polymerizedpetroleum hydrocarbons. Functionalized polymers are well known in theart and include copolymers such as styrene-co-maleic anhydride andcarboxylated polyolefins such as maleated amorphous, polypropylenes.Aromatic resins are generally aromatic modified hydrocarbons, such asNEVEX 100 from Neville Chemical Company. Terpene resins are generallypolymeric, resinous materials including the dimers as well as higherpolymers obtained by polymerization and/or copolymerization of terpenehydrocarbons such as the alicyclic, monocyclic, and bicyclicmonoterpenes and their mixtures, including allo-ocimene, carene,isomerized pinene, pinene, dipentene, terpinene, terpinolene, limonene,turpentine, a terpene cut of fraction, and various other terpenes.Commercially available tackifying resins of the terpene type include theZONAREZ terpene B-series and 7000 series from Arizona Chemical. Alsoincluded are the rosin esters with acid numbers above 5 such as theZONATAC resins from Arizona Chemical. Particularly useful materials areterpene mixtures containing a mixture of sulphate terpene, and at least20 percent of at least one other terpene selected from the groupconsisting of pinene, limonene, or dipentene. Rosins include gum rosins,wood rosins, tall oil rosins (e.g. FORAL AX from Hercules Incorporated)and hydrogenated rosins (e.g. PERMOLYN tackifiers also from HerculesIncorporated).

Depending on the end-use application and, particularly for usesrequiring pressure sensitive properties, various compatible plasticizingor extending oils can also be present in the composition to soften andplasticize the composition. Amounts of these oils are preferably about 1to 30 percent by weight, based on the total weight of the adhesiveformulation, more preferably 5 to 15 weight percent, with about 10weight percent being most preferred. Preferred compatible oils includenaphthenic oils; paraffinic oils (such as SHELL FLEX 371 from ShellChemical Company, a naphthenic/paraffinic blend); phthalate oils such asdioctyl phthalate; liquid polyesters such as DYNACOL 720 from Huls;dibenzoates such as dipropylene glycol dibenzoate (e.g., BENZOFLEX 9-88available commercially from Velsicol); isobutyrates (e.g., TXIB,available from Eastman Chemical Company); low molecular weightpoly(ethylene glycols) and derivatives thereof such as the phenyl etherof poly(ethylene glycol) (e.g., PYCAL 95 available commercially fromICI); liquid rosin derivatives having Ring and Ball melting points belowabout 60° C. such as the methyl ester of hydrogenated rosin (e.g.,HERCOLYN D from Hercules); liquid hydrocarbon resin such as WINGTAC fromGoodyear Chemical Company; mineral oils such as the TUFFLO series fromArco Chemical; as well as vegetable and animal oils such as glycerylesters of fatty acids and polymerization products thereof.

Other applications conventionally employing adhesives based on thesepolylactide polymers may require the use of wax diluents in order toreduce the melt viscosity or cohesive characteristics of the hot meltadhesive compositions without appreciably decreasing their adhesivebonding characteristics. These waxes are often used in adhesives whichdo not exhibit pressure sensitive properties.

Suitable waxes include 12-hydroxystearamide wax, hydrogenated castoroil, oxidized synthetic waxes, poly(ethylene oxide) having a weightaverage molecular weight above about 1000 and functionalized syntheticwaxes such as carbonyl containing ESCOMER H101 from Exxon.

Some adhesive formulations described herein can contain both wax andextending oils components so that the presence of one or the other isnot mutually exclusive.

These adhesive compositions can also be modified to increase the RBSPand reduce cold flow by including additives such as precipitated calciumcarbonates and silicas such as fumed silica. A suitable fumed silicacomes from Cabot Corp. as CABOSIL.

The present copolyester composition can be modified with random oralternating styrenic copolymers useful in the compositions of thisinvention and may be prepared by any of the several methods availablefor their synthesis. For example, the copolymers may be obtained bysolution copolymerization directly from the respective monomers by theincremental additions of the more reactive monomer as taught by U.S.Pat. No. 2,971,939 or by a continuous recycle polymerization processdescribed in U.S. Pat. Nos. 2,769,804 and 2,989,517. Suitablecommercially available random or alternating copolymers include theDYLARK styrene/maleic anhydride copolymers. Suitable blocked copolymersfor example from Shell Chemical, include KRATON FG-1901X or KRATONFG-1921X linear styrene ethylene-l-butene styrene blocked copolymers. Informulating adhesives or sealants for use herein, the blocked copolymersshould be used of 5-20 percent, preferably 7-12 percent.

The copolyester adhesive raw material composition of this invention canbe prepared by adding one or more of the above modifiers to the branchedcopolyester, by blending with the copolyester at melt temperatures of177-200° C. and mixing until a homogeneous mixture is obtained. A cowlesstirrer provides effective mixing for these preparations.

The present water dispersible adhesive composition is an improvementover the water dispersible adhesive composition disclosed in copendingapplication 08/283,011 filed Jul. 29, 1994 and publication WO 95/18191.Disclosed in that publication and patent application are waterdispersible adhesive compositions that comprise a single component madeof a copolyester and a blend of linear and branched copolyesters. Thesingle component water dispersible adhesive composition as a rawmaterial comprises a branched water dispersible polyester compositionmade of the moieties of reaction products that are: a difunctionaldicarboxylic acid that is not a sulfomonomer; a difunctionalsulfomonomer containing at least one sulfonate group bonded to anaromatic ring; at least one diol or mixture of diols of the formulaH(--OCH₂ CH₂ --)_(n) OH with n being 2 to 20 and then an additional diolwhere n can be 2 to 500 in combination with 0 to 99 mol percent of apossible third diol or glycol that has two C--(R¹)₂ --OH groups when R¹is as defined above; an optional hydroxy carboxylic acid; and 0.1 to 40mol percent of a multifunctional reactant containing three functionalgroups.

The blend in this copending application SN 08/283,011 and publication oftwo different polyesters comprises: 20 to 80 weight percent of a linearwater-dispersible polyester. This linear polyester is made of adifunctional dicarboxylic acid that is not a sulfomonomer; at least onedifunctional sulfomonomer containing one sulfonate group bonded to anaromatic ring; a diol or mixture of diols that contains 15 mol percentof the diol of formula H(--0CH₂ CH₂ --)_(n) OH with n being 2 to 20 and0.1 to 50 mol percent of a polyethylene glycol with n being 2 to 500;and an optional hydroxycarboxylic acid. The branched component of theblend being 20 to 80 weight percent that is made of the moieties of adifunctional carboxylic acid that is not a sulfomonomer: a difunctionalsulfomonomer containing at least one sulfonate group bonded to anaromatic ring; a difunctional reactant that is a glycol; an optionalhydrocarboxylic acid; and a multifunctional reactant containing at leastthree functional groups.

As with the copolyester adhesive raw material composition of the presentinvention the copolyester compositions disclosed in copendingapplication SN 08/283,011 can also be blended and formulated with theother additives and used as disclosed herein. However, the presentinvention is significantly improved over the disclosed compositions incopending application SN 08/283,011 in that the present copolyester isessentially odorless and is much more compatible at higherconcentrations with more additives such as tackifiers. The presentcopolyester is even very compatible with nonpolar additives. Althoughthe copolyester adhesive raw materials disclosed in application SN08/283,011 can be blended with tackifiers in concentrations of about 10to 50 weight percent, the lower IV copolyesters of about 0.2 dL/g arethe only ones that are completely compatible and dispersible in water atthe higher concentrations of tackifier. The copolyester compositions ofthe present invention can be blended with nonpolar e.g. hydrocarbontackifiers at much higher concentrations than possible with the priorcompositions and are compatible even when the copolyester compositionhas a much higher IV such as 0.4 dL/g. When using the higher IVcopolyester composition the resulting adhesive compositions are moresuitable adhesives with excellent strength while still being completelydispersible in water. Please see the examples.

The following examples are intended to illustrate the present inventionbut are not intended to limit the reasonable scope thereof.

EXAMPLES Example 1

Preparation of Branched Water-Dispersible Polyester

A 1000 mL round bottom flask equipped with a ground-glass head, agitatorshaft, nitrogen inlet, and a sidearm was charged with 158.2 grams (0.92moles) of 1,4-cyclohexanedicarboxylic acid, 23.7 grams (0.08 mole)dimethyl-5-sodiosulfoisophthalate, 95.4 grams (0.90 mole) diethyleneglycol, 43.2 grams (0.30 mole) 1,4-cyclohexanedimethanol, 6.70 grams(0.05 mole) trimethylol propane, and 1.17 ml of a 1.46 percent (w/v)solution of titanium isopropoxide in n-butanol. The flask was purgedwith nitrogen and immersed in a Belmont metal bath at 200° C. for 90minutes and 220° C. for an additional 90 minutes under a slow nitrogensweep with sufficient agitation. After elevating the temperature to 250°C. a vacuum of less than 0.5 mm was installed for 15 minutes to performthe polycondensation. The vacuum was then displaced with a nitrogenatmosphere and the polymer was allowed to cool after removing the flaskfrom the metal bath. An inherent viscosity of 0.41 dL/g was determinedfor the recovered polymer according to ASTM D3835-79 and a glasstransition temperature of 0° C. was obtained from thermal analysis byDSC. The polymer was odorless, clear, and nearly colorless.

Example 2

Preparation of Branched Water-Dispersible Polyester

This polyester was prepared as in Example 1 except that the vacuum wasfor 5 minutes. The resulting polymer was also odorless, clear, andnearly colorless. The inherent viscosity was 0.2 dL/g, and the glasstransition temperature was -10° C.

Example 3

Preparation of a Water-Dispersible Hot Melt Adhesive

A branched copolyester as prepared in Example 1 was blended withtackifier and oil and stirred at about 177° C. for 2 hours to producethe adhesive composition. The composition had a Tg of about -7° C. toabout 1° C. and a viscosity of 400 cP to about 20,000 centipoise at 350°F. (177° C.) as determined on a Brookfield HV: II Viscometer. Theformulation was odorless at mixing temperatures of 177° C. Theformulation had good adhesion to polyethylene and polypropylene films(ASTM D1876 T-Peel) and good tensile strength (ASTM 412 Test Method).The components of the adhesive and the results are reported in Table I.Into 100 ml of hot water (65-80° C.) at a pH of 7.8, were mixed 0.5grams of adhesive chips. Within 15 minutes under mild agitation theadhesive was completely dispersed in the water, forming a milky mixture.

The following tables (Table I, Table II, and Table III) compareproperties of the water-dispersible hot-melt adhesives according to thisinvention with typical hot-melt adhesive formulations in use today andone according to SN 08/283,011.

The tables and physical testing data, particularly T-peel adhesion,indicates that the polyester based adhesives demonstrate enhancedadhesion to olefin films and aluminum foil.

Example 4

Preparation of a Water-Dispersible Hot Melt Adhesive

The copolyester of Example 2 was blended as in Example 3 with the amountof the components shown in Table I. Comparisons are in the followingtables.

Example 5 (Comparative)

Preparation of Branched Water-Dispersible Polyester

A 1000 mL round bottom flask equipped with a ground-glass head, agitatorshaft, nitrogen inlet, and a sidearm was charged with 186.0 grams (0.92moles) of dimethyl-1,4-cyclohexanedicarboxylate, 23.7 grams (0.08 mole)dimethyl-5-sodiosulfoisophthalate, 95.4 grams (0.90 mole) diethyleneglycol, 43.2 grams (0.30 mole) 1,4-cyclohexanedimethanol, 6.70 grams(0.05 mole) trimethylol propane, and 1.17 ml of a 1.46 percent (w/v)solution of titanium isopropoxide in n-butanol. The flask was purgedwith nitrogen and immersed in a Belmont metal bath at 200° C. for 90minutes and 220° C. for an additional 90 minutes under a slow nitrogensweep with sufficient agitation. After elevating the temperature to 240°C. a vacuum of less than 0.5 mm was installed for 5 minutes to performthe polycondensation. The vacuum was then displaced with a nitrogenatmosphere and the polymer was allowed to cool after removing the flaskfrom the metal bath. An inherent viscosity of 0.2 dL/g was determinedfor the recovered polymer according to ASTM D3835-79 and a glasstransition temperature of +4° C. was obtained from thermal analysis byDSC. The polymer had an odor and was clear with a yellow color.

Example 6 (Comparative)

Preparation of a Water-Dispersible Hot Melt Adhesive

The copolyester as prepared in Example 5 was blended as in Example 3.The components and amounts are shown in Table II. The formulation had apredominant odor at a mixing temperature of 177° C. Comparisons are inthe following tables.

                  TABLE 1                                                         ______________________________________                                        Polyester Based Adhesive Formulations                                           Weight Percent                                                              ______________________________________                                        0.2 IV Polyester Example 2                                                                    40                                                              0.4 IV Polyester Example 1  40                                                Pentaerythritol ester (non Polar) 50 50 tackifier                             Dipropylene glycol dibenzoate 10 10 plasticizer                               Antioxidant .3 .3                                                             Tetra-bis-methylene-3(3,5-di-                                                 tert-butyl-4-hydroxyphenyl)                                                   propionate methane                                                            Brookfield Thermosel 177° C. 1650 18,400 centipoise                    Viscosity ASTM D3236 190° C. 910  5,380                                Ring and ball softening 71 97                                                 point ° C.                                                             ASTM E-28                                                                     Glass transition -7 -8                                                        DSC° C.                                                                Tensile strength mpa .02 .14                                                  ASTM D412                                                                     Peel Adhesion T-Peel                                                          ASTM D1876                                                                  Aluminum  g/mm      3.8      52                                                 polypropylene g/mm 4.4 11                                                     PET g/mm 10.3 19                                                            Water dispersion                                                                              disperse in                                                                              disperse in                                          1 gm in 100 ml of RT water less than 2 less than 8                             hours hours                                                                ______________________________________                                    

                                      TABLE II                                    __________________________________________________________________________    STARTING POINT FORMULATIONS                                                   __________________________________________________________________________                         COMMERCIAL EVA and                                           SIS Based                                                                   Polyester Based Hot Melt %/Wt. Hot Melt Wt./%                               __________________________________________________________________________    Polyester 0.2 IV Example 5                                                                     50  Elvax 220                                                                                 30%                                                                            --                                            Benzoflex 9-88 10 Kraton 1107 SIS --    20%                                   Foral AX 39.7 Eastotac H-100R 45 60                                           Irganox 1010 .10 Paraflint H-1 Wax 25 --                                      Cyanox 1212 .20 Shellflex 371 -- 20                                             Irganox 1010   0.1   0.1                                                    Viscosity @ 177° C. ASTM D3236 484 cps  860 cps 2230 cps                                                RBSP ° C. ASTM E-28 86°                                        C.  108° C. 87° C.            __________________________________________________________________________     ELVAX 220  ethylene vinyl acetate polymer from DuPont                         KRATON 1107  styrene block copolymer from Shell Chemical                      FORAL AX  wood rosin acid # of 140-160 from Hercules                          BENZOFLEX 9-88  dipropylene glycol dibenzoate plasticizer from Velsiol        Chemical                                                                      IRGANOX 1010  Antioxidant from Ciba Geigy                                     CYANOX 1212  Antioxidant from American Cyanamid                               EASTOTAC H100R  Tackifier from Eastman Chemical Company                       PARAFLINT H1 Wax  Moore and Munger                                            SHELLFLEX 371  Paraffinic/naphthenic oil from Shell Chemical             

    T-Peel Adhesion ASTM D1876                                                                     g/mm      g/mm)  g/mm                                        __________________________________________________________________________      PET  7.3  6.5 2.3                                                             PE 11.9 10.7 5.6                                                              PP 14.8 NA 7.1                                                                Water Dispersion 100% Dispersion -- --                                        1 gm in 100 ml of                                                             Tap Water, pH 7.8                                                             @ RT. (24 Hours)                                                            __________________________________________________________________________

Example 7 (Comparative)

An attempt was made to blend the polyester 0.2 IV of Example 5 with 30weight percent of the nonpolar tackifier pentaerythritol used in TableI. The blend was incompatible and phase separated in the molten state.

Example 8 (Comparative)

An attempt was also made to form an adhesive as above in Example 6 withthe same formulation and additives shown in Table II. The copolyesterbeing made as in Example 5 but with an IV of 0.4 dL/g (held under vacuumfor a longer period of time). The blend phase separated in the moltenstate.

Example 9 Aqueous Dispersion

The following results are from a 40 percent aqueous dispersion of thecopolyester of Example 2 having an IV of 0.2 and another dispersion ofthe copolyester of Example 1 having an IV of 0.4. The dispersions werecoated neat at a dry film thickness of 2 mil. T-Peel adhesion was thenperformed on each substrate.

                  TABLE III                                                       ______________________________________                                        Test Results:                                                                                0.2 IV    0.4 IV                                               ______________________________________                                        polyethylene   9.0    g/mm      6.3  g/mm                                       polypropylene 93.5 g/mm 7.3 g/mm                                              PET 110.9 g/mm 64.7 g/mm                                                    ______________________________________                                    

Example 10 Diaper Construction

The above 0.4 polyester dispersion of Example 9 was coated topolyethylene film and bonded to wood pulp from a "Huggies" trade namefor diaper from Kimberly Clark. The assembly was allowed to dryovernight. Five grams of this assembly was placed in 200 ml of tapwater. Within two hours, the polyester adhesive dispersed.

Five grams of the above diaper assembly was placed in a 0.2 molar ionicsolution (simulated body fluid). The bond assembly remained together.The adhesive did not disperse. The dispersibility in tap water andnon-dispersibility in an ionic solution is a unique advantage innonwoven articles.

*AATCC Test Method 15-1985

Alkaline solution

10 g NaCl

4 g ammonia carbonate

1 g disodium hydrogen phosphate

0.25 g histidine monohydrochloride

to 1 liter

We claim:
 1. An article of manufacture comprising an adhesivecomposition comprising:(a) 20 to 80 weight percent of a copolyestercomprising a branched water-dispersible polyester composition made ofthe reaction products;(I) 1.4-cyclohexane dicarboxylic acid (II) about 2to 40 mol percent, based on the total of all acid equivalence, of atleast one difunctional sulfomonomer containing at least one sulfonategroup bonded to an aromatic ring wherein the functional groups arecarboxyl or esters thereof; (III) at least one diol or a mixture ofdiols comprising:(A) about 0.1 to 85 mol percent, based on the total molpercent of diol moieties having the formula H(--OCH₂ CH₂ --)_(n) OHwherein n is 2 to about 20 provided that the mol percent of suchmoieties is inversely proportional to the value of n; (B) about 0.1 to15 mol percent, based on the total mol percent of diol moieties of apoly(ethylene glycol) having the formula H(--OCH₂ CH₂)_(n) OH wherein nis 2 to about 500, provided that the mol percent of such moieties isinversely proportional to the value of n; and (C) 0 to about 99 molpercent of the diol component being selected from the group consistingof glycols containing two --C(R¹)₂ --OH groups wherein R¹ in thereactant is a hydrogen atom, an alkyl of 1 to 5 carbon atoms, or an arylgroup of 6 to 10 carbon atoms; (IV) 0 to about 40 mol percent of ahydroxycarboxylic acid having one --C(R--)₂ --OH group, wherein R in thereactant is hydrogen or an alkyl group of 1 to 6 carbon atoms; and (V)about 0.5 to 40 mol percent of a "multifunctional" or "branch-including"reactant containing at least three functional groups selected fromhydroxyl, carboxyl, and mixtures thereof; the copolyester containingsubstantially equal mol proportions of acid equivalents (100 molpercent) and diol wherein the inherent viscosity is at least 0.1 dL/gmeasured in a 60/40 parts by weight solution of phenol/tetrachloroethaneat 25° C. and at a concentration of about 0.25 g of copolyester in 100ml of the solvent, the glass transition temperature T_(g) is no greaterthan 20° C. and the ring and ball softening point is at least 70° C. (b)about 2 to 60 weight percent of a tackifier selected from the groupconsisting of terpene resins, aromatic resins, aliphatic hydrocarbon,rosins, and polymers; (c) about 0 to 30 weight percent of an extendingoil selected from the group consisting of a paraffinic oils, naphthenicoils, liquid polyesters, liquid hydrocarbon resins, liquid rosins, lowmolecular weight polyethylene glycols, dibenzoates, isobutyrates,phthalate oils, animal oils, vegetable oils; and mineral oils; and (d)about 0.1 to about 2 weight percent of an antioxidant stabilizer;laminated between two substrates.
 2. The article of manufactureaccording to claim 1 wherein at least one of said substrates is selectedfrom the group consisting of paper, paperboard, and wood pulp.